Method and apparatus for forming concrete piles



March 25, 1969 J. R. HALL 3,434,294

METHOD AND APPARATUS FOR FORMING CONCRETE FILES Filed July 5, 1967 65 w 70 F164 w M JOHN R. HATZENTPB ATTOR NEYS United States Patent US. Cl. 61-53.6 Claims ABSTRACT OF THE DISCLOSURE A method of removing steel casing from caissons or piles as an incident to forming the piles, which includes the steps of hermetically sealing the installed casing adjacent to the bottom thereof and then pumping a column of concrete to the underside of the hermetically sealed casing, utilizing the energy of the elevation head and the pressure head to raise the casing at the rate at which the concrete is being pumped into the hole defined by the casing; and apparatus for carrying out this method.

Background of the invention In order to remove the steel casing from a caisson or pile, it is the conventional practice today to use a large crane to provide the force required to overcome the adhesion of the soil to the sides of the casing. Removal of the casing in this manner is very difiicult, and in some instances it is necessary to leave the casing in place, which represents a sizeable loss because of the relatively high cost of steel casing of this type. To further complicate this type of operation, concrete must be placed in the hole at a rate such that the level of the concrete remains above the bottom of the casing in order to prevent the sides of the hole from caving in. Even when the above conditions are fulfilled; there is no assurance that the sides will not cave in and ruin the caisson by pinching off a section of the concrete.

Efforts have been made in the past to provide other arrangements for removing the steel casings during the forming of concrete piles. One such method and apparatus is disclosed in United States Patent Nos. 754,375 and 754,376, granted Mar. 8, 1904 to W. C. Lyon. These patents teach a method of operation wherein a steel casing is initially filled with concrete, after which a cap is secured to the top of the casing and fluid under pres sure is introduced between the top of the concrete and the bottom of the casing cap, and sufficient pressure is applied to cause the casing to be withdrawn from the hole. This procedure has proved to be unsatisfactory, particularly where the concrete piles involved extend a substantial distance into the ground.

In the process proposed by Lyon, the fluid pressure applied for removing the casing must be sufiiciently great to overcome not only the friction of the earth acting on the outside of the casing, but also the friction of the concrete acting on the inside of the casing. The amount of friction between the concrete and the casing increases with time, and since in Lyons method the casing must be completely filled with concrete before removing, the amount of friction developed may be very large, and may be sufiieiently great to prevent removal of the casing even when the pile is a relatively short one.

Also, with respect to the Lyon method, as a consequence of the friction between the concrete and the casing, an arching effect is produced which reduces the amount of pressure that can be transmitted through the concrete. This condition is especially critical for long slender casing of the type used in present-day foundation constructions.

Another problem that exists with the Lyon method is that a delay or interruption in the supply of concrete may mean that pulling of the casing can not be accomplished due to the friction between the concrete and the casing. Thus, in the Lyon method, it is essential that the concrete be poured continuously and quite rapidly in order to enable the casing to be removed.

Summary of the inventi'om The present invention relates to an improved method of and apparatus for making concrete piles, and more particularly to such a method and an apparatus whereby a steel casing used in forming a concrete pile is removed at the same rate as the fluid concrete is introduced into the hole in the ground in which the pile is being formed.

The present invention has overcome the shortcomings of the prior art. According to one form of the present invention, a steel casing is provided which is adapted to be hermetically sealed at the bottom immediately prior to the step of introducing concrete into the hole. The concrete is pumped to the space below the sealed casing through a conduit so that the energy of the elevation head as well as the energy of the pressure head can be utilized to raise the casing at the rate at which the concrete is being pumped into the casing. The method and apparatus thus utilizes energy not heretofore available for removing steel casings and also functions in such a manner so as to eliminate completely the friction between the concrete and inner wall of the casing which was present in previous devices and methods employed in this field for removing steel casings. Also, this present method and apparatus enables the casing to be raised at the rate at which the concrete is pumped into the hole defined by the casing, and the friction forces which tend to hold the steel casing in place are not altered, if, for any reason, the source of supply of concrete is temporarily interrupted.

Accordingly, it is an object of the present invention to provide an improved method of forming concrete piles or caissons wherein the steel casings are removed from the hole in the ground as an incident to pouring the fluid concrete into the hole defined by the steel casings, and wherein optimum use is made of energy sources available to perform the function of removing the casing.

Other objects of this invention will appear in the following description and appended claims, reference being had to the acompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Brief description 0] the drawing FIGURE 1 illustrates schematically the forces that are in operation when utilizing certain prior art devices for removing a steel casing from a concrete pile;

FIGURE 2 is a view similar to that: of FIGURE 1, illustrating the arching effect that exists with respect to prior art devices;

FIGURE 3 is a schematic view partly in section, illustrating apparatus for carrying out the present invention; and

FIGURE 4 is an enlarged fragmentary sectional view illustrating details of the sealing member employed in the embodiment disclosed in FIGURE 3.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Description the preferred embodiments Attention is directed first to FIGS. 1 and 2 of the drawings for a brief description of some of the problems involved when using some of the prior art devices. As shown schematically in FIG. 1, a casing has been sealed at the top by means of a cap 12 and the arrows 14 represent the upward forces that are applied against the underside of the cap 12 when a fluid under pressure is introduced between the cap 12 and the concrete 16 which has been filled into the casing 10. In order for the forces 14 to raise the casing 10, it is necessary that they overcome the opposing friction forces acting on the outside of the casing 10, as represented by the arrows 18, and the friction forces exerted by the concrete against the inner wall of the casing 16, as represented by the arrows 20. Since the friction developed by the concrete 16 increases with time, any unnecessary delay in effecting removal of the casing 10 may result in the internal friction developed becoming large enough to prevent removal of the casing.

Further with respect to the prior art devices, as a consequence of the friction between the concrete and the casing, an arching effect is produced which reduces the amount of pressure that can be transmitted through the concrete. This condition is illustrated in FIG. 2 and is especially critical for long slender casings of the type now used in foundation constructions. As a rough guide, when the depth to diameter ratio is greater than five, arching may be a significant problem. As an example, if the pressure at the top of the concrete is increased by 100 pounds per square inch, the amount of pressure increase in the concrete at the bottom of the casing may only be pounds per square inch under a given condition. Thus, the net amount of pressure left to push the casing out of the ground may be drastically reduced. The arching effect is illustrated in FIG. 2 by the broken lines 22, and it will be understood by those skilled in the art that the forces 24 exerted at the top of the concrete pile are not equal and opposite to the reaction forces 26 exerted on the opposite end of the concrete pile 16. This is so because of the result of the arching effect that occurs in the concrete, so that much of the pressure exerted at 24 is transmitted to the casing 10, thus reducing substantially the magnitude of the reaction forces at 26.

The present invention has overcome the various problems existing with respect to the prior art devices, and for a description of a preferred embodiment of the invention, attention is directed to FIGS. 3 and 4 of the drawing. As there illustrated, a casing 30 is shown in a hole 32 in the ground. Positioned at a suitable location above the ground adjacent to the casing 30 is a conventional concrete pump 34 which has connected to its discharge outlet a hose or conduit 36 through which concrete can be pumped.

The steel casing 30 has secured adjacent to its lower end by welding or the like, a clamp ring 38, and secured to the clamp ring 38 so as to provide a hermetic seal is the cap 40. The latter has a fitting 42 to which the hose or conduit 36 is connected so that the concrete pump 34 can pump a column of concrete through the hose or conduit 36 into the space 44 below the bottom of the casing 30, which space 44 serves to receive concrete to provide a footing for the pile which is to be formed. As soon as the space 44 is filled with concrete, pressure from the concrete will be exerted against the bottom of the sealing member 40 and clamp ring 38 urging the casing 30 upwardly. This force will correspond to the elevation head of concrete measured by the height of the column of the concrete in the hose or conduit 36, and in addition, will reflect the pressure head measured by the pressure from the pump 34. Thus, the force acting on the bottom of the casing from the concrete pressure will be very sizable for the purpose of raising the casing 30 as the concrete is being introduced below the sealing member 40.

An example of typical forces and pressures involved in removing a steel casing is as follows:

Size of casing: 4 feet diameter, feet deep, /2 inch steel.

Weight of casing=24,000 lb.

Pressure in concrete at the bottom of the casing:

p =p (elevation head)+p (pressure head) =(100 ft.) (150 lb./ft. ft.) (l50 lb./ft. =l5,000+18,000 lb./ft.

Force at the bottom of the casing from the concrete pressure:

F=(l5,000+l8,000) pi 2 2 :4l5,000 1b. Net force available to push casing out of ground:

F ,=41s,o00-24,000=391,000 lb.

1 From Concrete Pump Manufacturer.

This is the force available to overcome the friction or adhesion between the soil and the casing.

When the casing is almost completely removed the amount of pressure available is less. For this case the force is 202,000 lb. when the bottom of the casing is at the top of the caisson. The decrease at any elevation is a linear proportion between the values calculated at the bottom and the top. Thus, when the casing is half way out of the caisson the force is 296,500 lb.

Normally, before any concrete is filled into the space 44, the cap 40 will be hermetically sealed to the ring 38, and therefore, means are provided for venting the air from the space 44 during the initial filling of this space with concrete. For this purpose a check valve 46 is provided which will be urged closed by the concrete 48 as the latter rises in the space 44. A remote control mechanism comprising the cable 50 and the pivotally mounted link 52 are provided to permit the operator to open the check valve 46 at this initial stage of the operation. A remote control mechanism is likewise connected to the lower end of the hose or conduit 36 including the cable 56 to provide the operator with a quick disconnect means for disconnecting the hose 36 from the fitting 42.

The cap 40 is also provided with means for raising and lowering it, including the cable 58 which is suitably connected to the top of the cap 40 by means of the cables 60. This arrangement allows the operator to lower the cap 40 into place after excavation of the footing space 44.

As previously indicated, any suitable clamping arrangement may be used for securing the cap 40 in a hermetically sealed relationship with respect to the casing 30. Referring to FIG. 4, one such arrangement will be described. The cap 40 has an annular groove in which is located an O-ring 62 adapted to engage the clamp ring 38 in sealing relationship. The clamping ring 38 also contains an annular shoulder 64 on which the cap 40 is adapted to be seated and retained in place by the clamping mechanisms 66. This is accomplished by movement of the clamps 68 radially outwardly to the position shown in FIG. 4 by actuation of the attached pistons 70, which are pneumatically actuated from a source of air pressure remotely located and supplied through the hose 72. Hose 74 is provided for moving the pistons and thereby the clamps 68 radially inwardly to an unlocked position.

In operation, the casing 30 is lowered as the hole is being excavated and finally the space 44 is excavated for the footing for the pile. The cap 40 is then lowered into position and the clamping mechanisms 66 are actuated to secure the cap 40 to the clamp ring 38. The fluid concrete is then pumped into space 44 and check valve 46 is held open to vent air therefrom until the concrete has filled space 44 at which time the concrete will urge the valve 46 closed. An additional concrete is pumped to the underside of cap 40, the forces from the elevation and pressure heads of concrete will lift the casing 30, overcoming the frictional forces on the outside of casing 30 which oppose such movement, and the casing will be raised at the same rate as the concrete fills the hole. This arrangement will permit interruption of the supply of concrete without impeding subsequent operations when the pumping of concrete is resumed. Also, because the concrete is maintained under pressure, this arrangement assures a sound pile which has not been rendered imperfect by virtue of earth pinching or partially pinching off the wet or fluid concrete.

Having thus described my invention, I claim:

1. A method for forming a concrete pile and simultaneously removing the casing from the hole in the ground in which the casing is positioned for the purpose of form- 'ing the pile, comprising the steps of hermetically sealing the casing adjacent to its bottom by lowering a cap to a position adjacent to the bottom of the casing and then securing said cap to the casing to provide a space between the bottom of the hole and the underside of the cap, pumping an enclosed column of fluid concrete under pressure from a source above the ground through said cap into the space between the bottom of the hole and the underside of the cap so as to utilize the pressure head and the elevation head of the concrete to exert upward pressure on said cap to lift the casing from the hole at the rate the concrete is pumped into the hole.

2. A method according to claim 1, wherein said cap is secured to said casing by pneumatically actuating a clamping mechanism.

3. A method according to claim 1, including the step of venting entrapped air from below said hermetically sealed casing when concrete is initially introduced into the hole below the hermetic seal.

4. Apparatus for making a concrete pile comprising a cylindrical casing having cap retaining means at its lower end, a closure cap adapted to be secured to said cap retaining means for elfecting a hermetically sealed closure of the lower end of said casing, vent means for venting air from below said cap, and means for pumping an enclosed column of concrete from above said casing through said cap to the underside of the latter, said means includ ing a concrete pump and a conduit extending from said pump to the underside of said cap.

5. Apparatus for making a concrete pile according to claim 4, wherein said vent means comprises a check valve operable to close when concrete is pumped against the underside of said cap, and remote control means for opening said valve.

6. Apparatus for making a concrete pile according to claim 4, wherein said cap retaining means includes a clamp ring integrally secured to said casing, and said cap includes a remotely controlled clamping mechanism for clamping said ring.

7. Apparatus for making a concrete pile according to I References Cited UNITED STATES PATENTS 1,831,209 11/1931 Thornley et al 61-53.66 1,904,079 4/ 1933 Powell 61-5364 X 2,775,869 1/1957 Pointer 61-465 FOREIGN PATENTS 428,119 6/1911 France. 286,333 8/1915 Germany.

JACOB SHAPIRO, Primary Examiner.

US. Cl. X.R. 6l53 .64, 63 

